Scrim for seams and joins of papermaking fabric

ABSTRACT

A papermachine fabric includes a base fabric and a strip of material covering a join or seam of the base fabric. The strip of material has an edge with a plurality of crenulations therein.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a non-provisional application based upon U.S. provisional patentapplication Ser. No. 60/752,069, entitled “IMPROVED SCRIM FOR SEAMS ANDJOINS”, filed Dec. 20, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scrim, and, more particularly, to ascrim used to cover a join or seam of a papermaking fabric.

2. Description of the Related Art

Scrims are known to reinforce joins and seams in press fabricapplications. Scrims provide, for example, fiber bonding adhesion, extrastrength, and extra wear resistance. U.S. Pat. No. 6,712,100 describesthe use of a scrim referred to as a strip of flow resistant materialthat is disposed over a seam regions, straddling it by an amount in therange from 0.5 to 2.0 inches and is attached thereto by sewing or by anadhesive.

A fibrous web is formed upon a papermaking forming fabric by thedeposition of a fibrous slurry, which includes an aqueous dispersion ofcellulose fibers on the forming fabric. A significant amount of water isremoved from the aqueous fiber web by the drainage from the slurrythrough the forming fabric, leaving the fibrous web on the surface ofthe forming fabric. The web is directed through press sections, whichmay include press nips and shoe presses often between two press fabrics.The web then proceeds to a dryer section, where the web is directed in acircuitous path around a series of drums that provide heat to theforming web for the removal of water therefrom.

The fabrics utilized in the papermaking include forming fabrics, pressfabrics and dryer fabrics, all of which are in the form of endless loopsin the papermaking machine, and they function as a conveyor of the web.

A seam or join, which is used to close the ends of a fabric into anendless construct during installation on the papermaking machine,represents a discontinuity in an otherwise uniform construct of thepress fabric. The presence of the seam substantially increases themarking that occur on the forming paper sheet, particularly as it isconveyed through a press nip.

A disadvantage of scrims include that there is locally added mass andcaliper to the seam area of the fabric. This results in differentperformance of the fabric proximate to the scrim, for example, sheetmarking, bounce in the press nip.

What is needed in the art is a scrim that reduces or eliminates sheetmarking and/or press nip bounce.

SUMMARY OF THE INVENTION

The present invention provides a scrim for covering a join or seam in apapermaking fabric.

The invention in one form is directed to a paper machine fabric,including a base fabric having a join or a seam, and a strip of materialcovering the join or seam. The strip of material has an edge with aplurality of crenulations.

An advantage of the present invention is that the scrim is less likelyto cause performance issues with the papermaking fabric.

Another advantage of the present invention is that even if a relativelywide scrim material is used there are minimal performance issuesassociated therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a perspective partially sectioned view of a papermaking fabricusing an embodiment of the scrim of the present invention;

FIG. 2 is an illustration of another embodiment of a scrim of thepresent invention;

FIG. 3 is an illustration of yet another embodiment of a scrim of thepresent invention;

FIG. 4 is an illustration of yet another embodiment of a scrim of thepresent invention;

FIG. 5 is an illustration of yet another embodiment of a scrim of thepresent invention;

FIG. 6 illustrates still yet another embodiment of a scrim of thepresent invention;

FIG. 7 is an illustration of a further embodiment of a scrim of thepresent invention; and

FIG. 8 is an illustration of still yet another embodiment of a scrim ofthe present invention.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate embodiments of the invention and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there isshown a fabric assembly 10 including a base fabric 12 and a strip ofmaterial 14 also known as a scrim 14. For ease of illustration, layersof fabric assembly 10 that may be added to that which has beenillustrated have not been shown and could include woven and non-wovenfabrics and fibers that are attached to base fabric 12 and/or scrim 14.An end 16 of base fabric 12 and an end 18 are joined together at 20 toform join 20 or seam 20. Seam 20 is formed by any manner known in thejoining of end 16 and end 18 of fabric 12. Scrim 14 is connected to basefabric 12 mechanically by needling, sewing, adhesives and/or a meltingoperation.

Scrim 14 has edges that are not straight, narrow, rectangular strips asthose used in the prior art. A relatively wide scrim is used and thesides are crenulated, for example crenulations 22 and 24. Thecrenulations may be circular, semi-circular, sinusoidal, square,triangular, trapezoidal and/or angular in shape. The crenulations occurin a repeating or in a random/irregular fashion. Scrim 14 should be morethan approximately 1 inch wide, but less than approximately 24 incheswide. Preferably, scrim 14 should be approximately 2 inches wide to 16inches wide. The indentions of the crenulations are approximately 5% to30% in depth as compared to the total width of scrim 14 or at least aminimum of 0.10 inch. An advantage of these indentations is that itminimizes the caliper/mass transition as the scrim passes through thenip resulting in a more uniform performance of the joined fabric. Thecrenulations also break up the border of the scrim so there is lesschance that the eye can detect its presence in the resulting web. Thisis ultimately reflected in the formed paper web resulting in lessvisible marking.

Now, additionally referring to FIGS. 2-8 there are illustrated some ofthe numerous crenulation possibilities. For example, in FIG. 2 there isdepicted a scrim 14 having a crenluation 26 and a straight side 28.Crenulations 26 are regularly spaced between end A and end B. Side 28,defined as an edge CD is not crenulated. An imaginary line connecting ABis generally parallel to CD. Lines AD and BC may or may not be parallel.The result is a shape ABCD that is a polygon, which can be substantiallyrectangular, substantially trapezoidal, and if AD is sufficiently narrowsubstantially triangular.

FIG. 3 depicts a portion of a scrim where both side edges are crenulatedas shown as crenulation 30 and crenulation 32. Both crenulation 30 and32 are regularly spaced and may be substantially a mirror image of eachother.

FIG. 4 depicts a scrim 14 where crenulations 34 and 36 are curvedcrenulations. Crenulations 34 and 36 are illustrated as being in phasewith each other contrary to those illustrated in FIG. 3. FIGS. 3 and 4each illustrate crenulations that are a pattern having regular spacingof the repeated pattern.

FIG. 5 depicts a scrim 14 having crenulations 38 and 40 that areirregular in spacing as well as irregular in shape. There is no symmetrybetween crenulation 38 and 40 and seemingly no pattern of repetition.

FIG. 6 depicts a scrim 14 having crenulations 42 and 44, similar to FIG.3. However, the crenulations of FIG. 6 extend in both directionsrelative to imaginary lines AB and DC. In a similar fashion crenulations46 and 48 of FIG. 7 illustrate a repeating shape of irregular spacing ofcrenulations entirely on one side of imaginary line AB and extendingoutside of imaginary line AB, while crenulations 48 extend in bothdirections of an imaginary line CD.

In FIG. 8 a scrim 14 is illustrated as being used over a pin-seam 20 orother type of join that has approximately a 15% to 45% open area, andmay be approximately 4 inches wide having a thickness of between 0.003inches to 0.010 inches thick. The scrim is made of a high strength andwear resistant material, such as a high-density polyethylene, polyesteror polyurethane. A low melt adhesive layer, like Ethylene Vinyl Acetate(EVA), may be coated on the scrim to improve fiber bonding of scrim 14to fabric 12. Crenulations 50 and 52 are a repeated pattern ofsemi-circular shape approximately 0.5 inches deep and spacedapproximately 1 inch apart. The permeability of the finished fabricassembly 10 in the area of scrim 12 will typically be somewhat lowerthan base fabric 12 apart from scrim 14 by 3% to 15%.

Advantageously the use of scrim 14 prevents the cross-directional barthat is seen on fabrics with prior art scrims. The prior art scrims havecaused problems like press bounce, faster rate of filling and sheetmarking due to the added scrim material and also because of the abrupttransition caused by the shape of the scrim. The purpose of theindentions, which are shown as circular type shapes in FIG. 8, which areadvantageous because of the circular shapes, is that they distribute thecompressive load more uniformly and are as such less prone to cause avisible mark. The circular shapes provide a better pressure uniformityand mass/caliper/permeability transition from the body of base fabric 12to scrim 14 versus the prior art, straight, sudden boundary edge. Thissignificantly reduces the risk of the above-noted problems.

Crenulations 22, 24, 26, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50 and52 each have a peak and a valley associated therewith. The differencebetween the peak and the valley is a distance that is from 5% to 30% ofthe total width of scrim 14. The width of scrim 14 can be thought of asthe length from A to D or from B to C.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

1. A papermachine fabric, comprising: a base fabric having one of a joinand a seam; and a strip of material covering said join or said seam,said strip of material having an edge with a plurality of crenulations.2. The papermachine fabric of claim 1, wherein said crenulations are atleast one of regularly and irregularly spaced cutouts.
 3. Thepapermachine fabric of claim 2, wherein said crenulations are at leastone of regularly and irregularly shaped cutouts.
 4. The papermachinefabric of claim 3, wherein each said crenulation has a peak and avalley, said peak and said valley being apart from each other by adistance of at least 0.1 inch.
 5. The papermachine fabric of claim 4,wherein said distance is at least 0.5 inch.
 6. The papermachine fabricof claim 3, wherein said strip material has a thickness of betweenapproximately 0.003 inches and 0.010 inches.
 7. The papermachine fabricof claim 3, wherein said crenulations have a shape being at least one ofsemi-circular, sinusoidal, square, triangular and trapezoidal.
 8. Thepapermachine fabric of claim 3, wherein said strip material has a widthof between approximately 1 inch and 24 inches.
 9. The papermachinefabric of claim 8, wherein said width is between approximately 2 inchesand 16 inches.
 10. The papermachine fabric of claim 3, wherein said basefabric has a permeability and a combination of said base fabric and saidstrip of material have another permeability that is from approximately3% to 15% less than said permeability.
 11. The papermachine fabric ofclaim 4, wherein said strip material has a width, said distance beingfrom approximately 5% to 30% of said width.
 12. The papermachine fabricof claim 3, wherein said strip material has an other edge opposite ofsaid edge, said other edge being one of crenulated and not crenulated.13. The papermachine fabric of claim 12, wherein said edge is generallyparallel to said other edge.
 14. The papermachine fabric of claim 12,wherein said edge is generally not parallel to said other edge.
 15. Ascrim for covering one of a join and a seam of a papermachine fabric,the scrim comprising a strip of material having an edge with a pluralityof crenulations.
 16. The scrim of claim 15, wherein said crenulationsare at least one of regularly and irregularly spaced cutouts.
 17. Thescrim of claim 16, wherein said crenulations are at least one ofregularly and irregularly shaped cutouts.
 18. The scrim of claim 17,wherein said crenulations have a shape being at least one ofsemi-circular, sinusoidal, square, triangular and trapezoidal.
 19. Thescrim of claim 17, wherein said base fabric has a permeability and acombination of said base fabric and said strip of material have anotherpermeability that is from approximately 3% to 15% less than saidpermeability.
 20. The scrim of claim 17, wherein said strip material hasa width, said crenulations having a distance from a peak to a valley,said distance being from approximately 5% to 30% of said width.